Select the reagent used in the rosenmund reaction.

Options

A. `H_2`
B. `Pd-baSO_4`
C. both (1) and both 2
D. none of these

Answer

To solve the question regarding the reagent used in the Rosenmund reaction, we can follow these steps:

### Step 1: Understand the Rosenmund Reaction
The Rosenmund reaction is a chemical reaction that involves the reduction of an acyl chloride to an aldehyde. This reaction is significant in organic chemistry for synthesizing aldehydes from acyl chlorides.

### Step 2: Identify the Reactants
In the Rosenmund reaction, the primary reactant is an acyl chloride (RCOCl). This compound will undergo reduction to form an aldehyde (RCHO).

### Step 3: Determine the Reagents Used
The reduction of acyl chloride to aldehyde in the Rosenmund reaction is typically carried out using hydrogen gas (H2) in the presence of a catalyst. The specific catalyst used in this reaction is palladium on barium sulfate (Pd/BaSO4).

### Step 4: Write the Overall Reaction
The overall reaction can be summarized as follows:
\[ \text{RCOCl} + \text{H}_2 \xrightarrow{\text{Pd/BaSO}_4} \text{RCHO} + \text{HCl} \]
Here, hydrogen is added to the acyl chloride, resulting in the formation of an aldehyde and hydrochloric acid (HCl) as a byproduct.

### Step 5: Select the Correct Reagent
From the information gathered, the reagent used in the Rosenmund reaction is:
- Hydrogen gas (H2)
- Palladium on barium sulfate (Pd/BaSO4)

Thus, the correct answer to the question is that both H2 and Pd/BaSO4 are needed for the Rosenmund reaction.

### Final Answer
The reagent used in the Rosenmund reaction is **H2 in the presence of Pd/BaSO4**.

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